What is this?

[Reef Monster]

My RSR 250 tank has been running for a little under or at 2 months now. I ran the first month without lights on. This stuff started growing around 2 weeks ago. I vacuumed the sand, brushed the rocks off and did 25% water change and it came right back. Test kit on my water before the water change was:

pH: 8.2
Ammonia: 0
Nitrite: 0.05
Nitrate: 2
Phosphorous: 0.046 ppm

I have 6 fish. I feed mostly pellets and fish net the left overs. I use Red Sea blue bucket salt at 35 ppt and keep my water at 78. I also use radion XR15 lights (2) and run them from 12pm to 10pm with the coral labs softies/lps setting. I’m new to this hobby so advice is much appreciated.

 

[smellytunic]

Looks like diatoms. Pretty normal for new tanks. It gets ugly before it gets better. Some ways to manage it. Clean up crews help but will not really eliminate it. Run a skimmer, change filter socks frequently, clean glass and sand, lower cool whites on lighting for a bit. It will usually run its course on it’s own. If after a week or two it is still spreading then look into water sources for top off and new salt water. It feeds off silicates that come from two common sources new sand or water supply

 

[dansreef]

Looks to be a diatom bloom... Your tank is really new...and it is going to go through all sorts of uglies. That is the tank maturing. You need to be patient and let the tank run its course. Get your Nitrites to zero... I wouldn't worry about vacuuming these off... they will die off in due time. You will start to see green algae replace them as well as coraline algae in all different colors... and that is good.Don'tt get too concerned. It will take months to get through all these changes.... or the uglies...

You can go get some snails and other clean up crew... to keep the diatoms and algae in check.

 

[Reef Monster]

Thanks guys. I was worried about it being cyano because of the phosphate level. When I change the water is it ok if some of the rocks are exposed to air? It’s a 55 gallon tank with a 10 gal sump so when I change 20 gallons, the rock at the top is exposed briefly.

 

[Mariette]

Regular run of the mill “uglies”. Part of the process. No need to do anything. Wait it out

 

[smellytunic]

Thanks guys. I was worried about it being cyano because of the phosphate level. When I change the water is it ok if some of the rocks are exposed to air? It’s a 55 gallon tank with a 10 gal sump so when I change 20 gallons, the rock at the top is exposed briefly.

No problem if it is just the rock that is exposed for a bit